Laboratory film is typically a waterproof plastic or parafilm-type sheet material, which stretches and adheres to smooth surfaces when it is wrapped under tension over and around openings, joints and the like. It is used universally in laboratories in great quantities. Being adherent and being supplied from a roll, it is backed by a loosely adherent, thin, strong release paper. One such laboratory film is known as Parafilm "M" supplied by the American Can Company of Greenwich, Conn.
Being supplied in rolls, requires that the film be cut off, a piece at a time, including the backing paper. The two layers, often called a bi-layer, are, as a single sheet normally pulled from the roll which is supplied in cardboard dispenser boxes. It is cut to the desired length, often by scissors.
There are also commercial dispensers for films of this type. One type incorporates a lever operated, razor cutter. The film is pulled out to the desired length, and while pulling on the film to cause tension, the operator moves a lever on the box. This causes the razor blade to traverse and cut the film, including the backing. However, the device requires a two-handed operation, and is generally cumbersome since its use requires the operator to lay down the object to which he desires to apply the film, such as a test tube or other vial.
One problem in cutting paper-backed laboratory film with a scissors is that the film is caused to adhere to the backing along the line of cut, since the scissors cut involves two metal blades engaging each other and squeezing the film and paper together.
One of the objects of this invention is to provide a cutting mechanism, wherein the cutting blade engages only the film and its backing, not another metal object.
The film is generally provided on a cardboard roll, which is mounted for rotation in a commercial cardboard box. The film is pulled from the box while the roll rotates. Given this geometry, another object of this invention is to provide a sheet cutting and dispensing device which does not require the roll of film to be removed from its supply box, and where the box, including the film, can be placed in the dispenser.
The supply box need never be opened, which assures that the film will be clean and fresh each time a piece is cut from the roll.
Another object of this invention is to provide a cutting and dispensing device, which can be operated solely with one hand.